X-y-recorder



G. KEINATH 2,400,82

X-Y-RECORDER Filed Dec. 24, 1942 4 sheets-sheet 1 May 2l, 1946.

226 INI/ENTOR.

GEORGE fE/A/A 7H.

ATTORNEY May 2l, 1946.

G. KEINATHI X-Y-RECORDER Filed Dec. 24, 1942 4 Sheets-Sheet 2 INI/EN TOR. GEORGE /fE/A/A 7H.

A TTOPNEK X-Y-RECORDER Filed Dec. 24, 1942' 4 Sheets-Sheet 3 INVENTOR. G50/PGE Kev/VA 7H.

ATTORNEY.

May 2l, 1946.

- INVEN TOR. G50/PGE /fE//VA 7H.

A TTOJPNEK Patented May 21, 1946 UNITED STATES PATENT OFFICE X-Y-BECORDER George Keinath, Larohmont, N. Y. Application December 24, 1942, Serial No. 470,087

21 Claims.

My invention refers to measuring systems for determining a function of two variable, measuring magnitudes or quantities for controlling an indicating, recording or control mechanism in accordance with'that function. More in particular, the invention is concerned with systems of the just-mentioned type in which the variation of neither of the two quantities is necessarily proportional to time. For instance, there are the requirements of indicating, recording, or using as a governing control the variations of anwelectric resistance in its functional relation to temperature, or the magnetic inductance of a ferromagnetic body in relation to the effective magnetic eld strength, the voltage drop along a resistance body as a function of an electric current, the temperature of steam relative to its pressure, or the viscosity of a liquid in dependence upon pressure or temperature, to mention only a few examples of phenomena whose variations or quantities are of interest with respect to the present invention.

IThe general problem of determining and recording a function of two variable magnitudes or quantities has found a partial solution in the .so-called X-Y-recorders in which a recording drum is revolved in dependence upon one of the magnitudes while the recording stylus moves under the control of the other thereby tracing a curve representing the function to be determined. However, while the above-stated operating principle of the known X-Y-recorders appears simple at rst glance, the practical realization and according to the prior art involved difilculties and complications as to the necessary mechanical apparatus, as well as considerable limitations as to the uses and ranges of magnitudes for which this type recorder could heretofore be applied. These drawbacks are due to the rather intricate and heavy mechanism, involving the transmission of the relatively great forces and torques required in the known X-Y-recording apparatus, as well as to the electric measuring systems used for controlling the recording mechanism in accordance with the magnitudes to be determined.

It is an object of my invention to provide measuring systems for controlling an indicating, recording or control mechanism in dependence upon two variable magnitudes or quantities (both terms being used interchangeably in this specification) which reduce or avoid the above-mentioned shortcomings of the known X-Yf-type recorders. An object, more specifically, is to simplify the mechanical apparatus required for the operation of such a system. Another object is to render the system sensitive to lower control magnitudes than heretofore properly applicable.

Still another object deals with rendering the design and operation of such a system predominantly electrical, thereby contributing to simpliiication in mechanical respect and increased accuracy and reliability of operation. Other objects will be mentioned in a later place.

According to the invention, two adjustable measuring devices are provided for controlling two respective relays in accordance with the two controll quantities supplied to these devices respectively. The adjustment of one device is cyclically varied by drive means in synchronism with a cyclical motion of a member of the mechanism, for instance a recorder drum, and the adjustment of the other measuring device is varied by actuating means in synchronism with the motion of another member of the mechanism, such as a recorder stylus, cooperating with the firstmentioned mechanism member. It is essential in this aspect of the invention that the two cooperative mechanism members be ineffective, i. e., run idle, -during the just-mentioned synchronous motions and .be rendered effective only when both relays have passed into responsive condition, an

electric pilot circuit being provided between the relays and the mechanism to transmit a control impulse at the proper moment.

3l) According to another feature of the invention,

one of the above-mentioned synchronous drive or actuating means operates periodically while the other proceeds stepwise or, in general, in accordance with a given program of progression so that each step of progression involves at least one cycle of the periodic drive. In another aspect of the invention, one of the two drive or actuating means is operated in a cycle of a chosen period or recurring with a chosen frequency while the other is automatically governed by the operation of the mechanism to be controlled.

Since these and other objects and features of the invention are more easily understood in connection with concrete examples, reference is made to the embodiments shown in drawings before explaining other purposes and characteristics of the invention.

Figs. 1, 2 and 3 of the drawings refer to a single recording system, Fig. 1 showing some details, Fig. 2 a complete diagram of the system including its essential electrical and mechanical elements, and Fig. 3 a recording sheet with a record representative of those obtained by the system.

Figs. 4, 5 and 6 illustrate three further'embodiments, respectively, each designed as a recorder system.

Fig. 7 shows diagrammatically a modiiled actutrated system is intended to measure and record the change in the electrical resistance of a resistor in dependence upon its temperature.

According to Fig. l. the resistance bdy 2|| under investigation is connected with terminals A and B and submerged in an insulating bath in a heating vessel 22| provided with an electric heating element 222. The element 222 is connected with a current source 224 through a rheostat 222 which permits increasing and decreasing the bath temperature' at will. A resistance thermometer. 22|, connected to terminals C and D, is also submerged in the bath for measuring the bath temperature.

The elements 2||l A, B and 22|, C, D respectively are connected in a measuring system as shown in Fig. 2 where the same reference characters are used for indicating the just-mentioned elements in their relation to the other parts of the system.

The system contains two separately adjustable measuring devices both consisting in this embodiment of balanceable electric circuits in the form ot Wheatstone bridges.

The nrst bridge serves ior determining the resistance magnitude of resistance body 2|| and includes a constant resistance 2|2 and a potentio- Y metric balancing resistor 2 |2 which is of circular design and rovided with a rotary slide contact 2|4. The de contact 2|4 is connected in the aero branch or bridge diagonal 2|9 of the circuit in seriesJ with the coil 2|5' of a moving-coil galvanometer 2|! serving as a relay. The coil 2li' is rotatably mounted onsl pin I between the poles oi' a permanent magnet 2li' and controls a movable contact 2|. Numerals 2|1 and 2|2 denote the Vstationary contacts to be engaged by the movable contact. The bridge circuit is connected by leads 214 and 215 with an energizing current source 21| of either direct current or alternating current.

When the potentiometer contact 2|4 performs one cycle of rotary motion, it passes through a position where the bridge circuit is balanced so that the diagonal current in branch 2|2 passes through zero andchanges its direction. In the moment of balance, the relay 2|2 switches its movable contact 2|2 from stationary contact 2|1 to contact 2|2, or vice versa, depending uponv the direction of rotation of slide contact 2|4. This elect may occur at diiierent positions oi' the slide contact relative w theJ resistor zn, depending upon the instantaneous magnitude of the variable resistance body 2| Hence, the angular position oi' the slide contact 2|4 at the time of the switching-over of relay 2|! is indicative ofthe resistance magnitude to be measured.`

The second bridge circuit serves to measure the temperature as represented by the variable resistance of the resistance thermometer body 22|. 'I'his bridge includes also a constant resist- `ance 222 and a potentiometrlc balancing resistor 222, and is energized through leads 212 and 211 from the current source 21|. The potentiometer resistor 222 is of straight construction and co operates with a reciprocatory slide contact 224 disposed in the diagonal 222 of the bridge in series arrangement with the moving coil 222 oi a galvanometric relay 225. The coil 225 is mounted on a rotatable pin 25 between the poles of a magnet 226' and has a movable contact 222 cooperating with two stationary contacts 221 and 222. The movable contact changes its position when the bridge passes through the balance condition. that is, when the adjustment of the balancing potentiometric device is indicative oi' the temperature magnitude to be determined.

Associated with the two adjustable measuring devices described in the foregoing is a recording mechanism with two cooperative members consisting o! a reciprocatory stylus 244 and a revolving drum for accommodating a recording sheet. The drum 245 and the potentiometer contact 2|4 are rotated or actuated periodically and insynchronism with each other. 'I'he drive meansi'or eilecting the synchronous motion include anelectric motor 22| fed from the current source 21| through leads 212 and connected with thecontact 2|4 and the recorder drum 245 by shafts 222 and 246 respectively. The recorder stylus 244 and the potentiometer contact 224 are likewise operated in synchronlsm with each other, and to this yend are attached to a. holder 243 actuated by a worm shaft 242 which in turn is driven by a mo toric device 24|. However, while the periodic drive eifected by the motor 23| operates in continuous motion, the actuating device 24| is of the type of a stenswitch, i. e., it operates intermittently, advancingthe contact assembly oi' members 224, 243, 244 step by step over a graduated range of progression. As will be set forth in a later place, the operating period of the actuating device 24| and the members driven thereby is longer than that of the drive 23|, so that the rotating potentiometer contact 2|4 completes its cycle once or several times during each step of progression of the intermittent actuation.

The recorder mechanism is so designed that the motion of stylus and drum does not in itself produceva record on the sheet placed on the drum. An electric pilot circuit is provided for controlling the writing operation of the stylus so as to limit it to selected moments or intervals. An ink recorder having the flow of ink controlled by the electric circuit could be used for this purpose. However, an especially simple and reliable operation is obtained if the stylus and drum members form electrodes to pass, when energized, a discharge current through an electrolytic, i. e., current-responsive, recording sheet, thereby producing a recording mark on the sheet only at the time of the current ilow. This type recorder is used in the illustrated system, an electric pilot circuit being connected with the two electrode members, i. e., the drum and the stylus, of the recorder, as will be explainedpresently.

The movable contact 2li of the relay 2|! is connected with one pole of a` capacitor 222. The stationary contact 2|1 oi the same relay lies in series with a. current-limiting resistor 222 and a current source 22| which in turn is connected to the other pole of the capacitor 222. When the movable contact 2|2 engages the stationary contact 2|1, thev capacitor is charged from the current source 22|.- A connection 224 leads from the stationary contact 2 I2 to the movable contact 222 of the other relay 222. The stationary contact m er remy 22s is connected by a aad zas with the actuating device 24|; another lead 286 connects the latter with the drum 245 of the recorder whose stylus 244 is connected through lead 281 with the capacitor 283. Connected between the capacitor 283 and the other stationary contact 228 of relay 225 is a discharge path 288 which may contain a current-limiting resistor 280. The leads numbered 284 through 281 and the appertaining relay connections form the above-mentioned pilot circuit, as will be better apparent from the following description of the relay operation.

'I'he illustrated positions of both relays correspond to the inoperative condition of the pilot circuit. As long as during each rotation of contact member 2 |4, beginning from its initial position, the member has not passed through the balance position, the relay contacts 2|5 and 2|'| remain engaged with each other so that the capacitor is charged but not in condition for discharge. When contact 2 |4 passes through its balance position, relay contact 2|6 switches over to contact ;2|8. Assuming that relay 225 is still in the illustrated position, the capacitor discharges itself immediately through the discharge path 288 closed over contacts 226 and 228. Hence, the discharge has no eiiect on the recorder and decays quickly while the potentiometer contact 2|4 continues its motion and the contact 2 |6 remains in engagement with Vcontact 2|8. However, if at vthe time of discharge the relay 225 has also responded to the passage through balance of the reciprocatory contact member 224 of the appertaining potentiometer, the short circuit through path 288 is eliminated and the discharge of the capacitor passes from lead 284 through contacts 225 and 228, then in engagement with each other, to lead 285, the actuating step switch 24| and the recorder members 245 and 244. As a result,-a recording mark is produced on the recording sheet.

As described, the actuating device 24| is also connected in the pilot circuit in order to be controlled thereby. Each discharge impulse passed through the recorder thus causes the device to move the assembly of members 224, 243 and 244 one step along their path of progression.

Reviewing the system as a whole, its operation will now be understood from the application exemplied in the following.

Let us assume that the container, bath and submerged elements, shown in Fig. l, are in cold condition and that the resistance-temperature characteristic of the resistance body 2|| is to be determined by recording a corresponding curve. We proceed by heating the bath up to a maximum temperature of say 300 centigrade by energizing the heater 202. At the beginning of the heating period, the drive motor 23| is set in operation so that the potentiometer contact 2|4 and the recorder drum 245 begin their periodical rotation and continue to operate during the entire heating and measuring period. The reciprocatory potentiometer contact 224 and the stylus 244 remain at irst stationary on the starting point,l for in- .stance at the right-hand side of their path of motion. In this position, the potentiometric balancing resistor 223 is contactedby member 224 at a point which corresponds to a temperature slightly above the initial bath temperature, the difference being, for instance, 3 centigrade. The rotating contact 2 |4 during its continuous travel will now pass through its balance point during each of its cycles. Each time this point is traversed, the relay 2I5 is actuated and the capacitor 288 discharged to be recharged after the completion of the cycle. However, as long as the temperature remains below that to which the contact 224 is adjusted. the resistance oi control element 22| is too low to balance its appertaining bridge circuit. Consequently, the relay 225 remains in the illustrated position so that the rst discharge of the capacitor, or several successive discharges pass through the short circuit path 288 and have no effect on the recorder and the step switch 24|. As soon as the temperature measured by control element 22| reaches the degree corresponding to the program point to which contact 224 'is adjusted, the appertainingy bridge passes through balance and causes the relay 225 to disconnect the path 288 While connecting the pilot lead 228 with the discharge circuit. 'I'he next discharge effected by relay 2|5 must now pass through the recorder and produce a. recording mark on the recording sheet. Immediately afterward, the step switch, also energized by the discharge current, moves the contact 224 and stylusl 244 one step forward to the second program point representing a higher degree of temperature, the difference being, for instance, again 3 centigrade. As a result, the relay 225 drops back to the original, illustrated position as soon as a recording mark is produced. In this moment, the slowly rising bath temperature lags behind that prescribed by the new position of the contact 224. Consequently, the next discharge, or several of them, will be ineffective until the control element 22|, responsive to the rising bathtemperature. is again in condition for balancing the bridge circuit. Then the relay 225 is actuated so that the next discharge issuing through relay 2|5 will produce a second recording mark while causing the potentiometer contact 224 to advance a further Vstep and the relay 225 to return to its initial position. This operation repeats itself until the desired measuring range is covered.

The curve thus recorded on the recording sheet is of the type shown in Fig. 3. This figure represents a sheet 205 taken from the recorder drum. The curve 205 is composed of a number of successive marks or points, each produced during one step of the above-described operation of the system. Since the angular position of the drum at the time of each discharge is correlated to that of the potentiometer contact 2|4 and hence indicative of the resistance value of body 2| and since the discharge is effective only when the preadjusted position of the potentiometer contact 224 and the stylus 244 corresponds to the temperature measured by element 22 each mark, as to its location in the coordinate system of the recorded diagram, represents a function of both control magnitudes. The curve 20G is a locus of such functions and hence representative of the characteristic to be determined.

The accuracy of measurement depends on the operating speed of the rotating potentiometer relative to the rate yof change of the temperature to be measured. That is, the accuracy can be increased within wide limits by increasing the speed of rotation or lengthening the heating period, or both. The speed of rotation may easily be kept at such a value as to permit measuring rather fast-changing phenomena, lasting, for instance, but a few minutes or seconds. The accuracy of operation depends also on the gradation of the step drive and its appertaining potentiometer. The higher the number of steps, a corresponding rotating speed of contact 2|4 being provided for,

to the controlling phenomena. For the aboveexempliiled purpose, a gradation into 50 to 100 steps, for instance 100 steps each for a temperature difference of 3 centigrade, may be chosen for a temperature range of to 300 centigrade.

After the completion of the recording operation, the assembly of members 224, 243 and 244 is returned into its original position in order to reset the system for another recording. If it is required to measure changes in both directions, however. the actuating means are preferably made reversible so that the assembly 224, 243 and 244 is stepwise returned while operating the system in the same manner as described above, except that now the bath with its submerged elements is now permitted to cool to a low temperature. The reversal can be obtained by using a polarized reversible step switch or by a mechanical reversing gear of which many types are available. It is preferable to reverse either the polarity of relay 224 or the connections or contacts 221 and 223 together with the reversal of the stylus motion. An example of reversing means, applicable in the system of Fig. 2, will be described more in detail in connection with Fig. 4.

In cases where an indication of the duration of the measuring operation is desired, the recorder may be provided with a time-marking device. Fig. 2 shows such a device. It contains a second stylus electrode 234 attached to a holder 233 which is moved along the drum 245 in proportion to time by means of a threaded shaft 232 operated by a motor 25| connected through leads 255 with the current source 21|. In intervals of equal duration of say 5 or 10 seconds, a current discharge is passed from the stylus 254 onto the recording sheet, producing time marks as shown at 231 in Fig. 3. If both motors 23| and 23| are synchronous, the time marks appear in one row in parallel to the drum axis, and it is easy to place them on a convenient space of the recording sheet, preferably those for the upward movement separated from those for the downward movement, `merely by correspondingly selecting the phase position of the time-marking discharges relative to the rotation cf the drum. A contactor (not shown) driven by motor 23| over an angularly displaceable control cam may be used for this purpose.

It will be apparent that the construction and operation of a measuring system of the abovedescribed type remains the same if the temperature variation is measured by the arrangement having the periodically operating potentiometer while the controlling resistance variation is effective in the arrangement having the stepwise actuated potentiometer. It will likewise be seen that not only resistance-temperature characteristics but any other phenomena can be caused to operate the system as long as these phenomena can be reduced to variations of an electric circuit member. However, it will be shown in the following that such systems are also applicable with any other electrical or non-electrical magnitudes capable of controlling a relay by a differential effect in cooperation with an independently variable adjusting element. The principles of construction and operation of the system, aside from the particular measuring purpose involved, are also capable of modification in various respects. This will be clear from the embodiments of Figs. 4 through 'I to be described hereinafter.

To facilitate a comparison of Figs. 4 through 'I with Fig. 2, and in order to permit shortening the the more closely will the recorded curve be similar description of these other embodiments, the lut two digits of the reference numerals employed in all ngures are equal when referring to functionally similar elements.

The system shown in Fig. 4 serves to record a function of two variable control magnitudes represented by corresponding resistance variations of two respectivev circuit elements 4I| and 42|.

The circuit element 4|| lies in a bridge circuit which contains also a constant resistor 4|! and a potentiometric balancing resistor 4|3 whose movable slide contact 4|4 is disposed in the aero branch 4|3 of the circuit in series connection with a relay 4I5. The relay is of the polarized type, a reversing switch 433 being provided in order to change the direction of operation of the relay.

445 represents the drum member and 444 the stylus member of a recorder. Both members form electrodes for passing a current discharge through the recording sheet, preferably of the electrolytic type, placed on the drum 445,

The stylus member 444 is connected with the potentiometer contact 4 I4 by means of a common holder 433 which is reciprocable along a straight guide 435. The holder 433 is coupled with an arm 435 journalled about the fulcrum 431 and in driving connection with a pitman 433 actuated by a synchronous motor 43| which is energized from the line 41| through leads 412. When in operation, the motor 43| causes the arm 433 to perform periodic oscillations thereby reciprocating the assembly of members 4|4, 433 and 444 along the recording drum 445 and the sheet placed thereon. During its periodic travel, the assembly passes through a position which at that particular moment is indicative of the resistance value of circuit element 4I| for the reasons previously explained with reference to Fig, 2. The relay 4|5 has a. movable contact 4|3 cooperating with two stationary contacts 4|1 and 4|3. The movable contact changes its position each time the potentiometer `contact 4|4 passes through the balance position.

The above-mentioned reversing switch or pole changer 433 is connected in the zero branch 4I3 so as to reverse the polarity of relay 4|5 when actuated. This switch is controlled by the reciprocating assembly of elements 435 and 433, for instance, by means of so-called end switches (not illustrated) so `as to effect a pole change each time the assembly reaches either end of its travel. As a result, the apparatus is operative in both directions of motion of the assembly.

The variable circuit element 42| is connected in a bridge circuit containing a constant resistor 422 and abalancing potentiometeric resistor 423 whose movable contact 424 is series connected with a second relay 425 in the zero branch 423 of theK bridge. Contact 424 is attached to a rotary arm 443 which is actuated through a connection 442 from an intermediate step drive 44|. A similar connection 445 causes the recorder drum 445 to rotate in synchronism with the contact 424. The relay 425 is actuated as soon as the resistance magnitude of circuit element 42| corresponds to the position of contact 424 relative to the potentiometric resistor 423. The movable contact 423 of relay 425 cooperates with stationary contacts 421 and 423 which are mnnected through a reversing switch 453 and lead 435 with the step drive which in turn is ccnl nected with the drum member 443 by a lead 433.

The pilot circuit thus formed is completed by s vation of the pilot circuit proper.

connection 481 leading from the styluselectrode lead 484 connecting the movable contact 428 of relay 425 also with the contact assembly of relay 4I5. A discharge' circuit containing'a current source 48|, a resistor 482 and a capacitor 483 is so connected with the contacts of relay 4|5 that the capacitor is charged when the relay is in non-responsive position and discharged into thev pilot circuit as soon as the relay assumes its responsive position. If, at the time of this action,

' a denite minimum requirement as to the voltage necessary i'or moving the movable contact 5|6 the relay 425 is also in responsive condition thereby connecting its movable contact 426l through the stationary contact 421 with the step drive and the recording device, a control impulse is passed through the pilot circuit thereby causing the stylus electrode to produce a mark on the recording sheet and at the same time moving the step drive one step forward as explained when describing the corresponding operation o f the system shown in Fig. 2. However, if at the moment of response of the relay 4I5 the second relay 425 is non-responsive, as is illustrated in Fig. 4, the discharge from capacitor 483 passes through a short-circuiting path 488 which contains a resistor 490. As a result, the discharge is now rendered ineffective as regards the oper- In order to ensure the just-mentioned function, the resistance of resistor 490 must be high as compared with that of the pilot circuit. Assuming, for instance, that the series resistance of the step drive and the recording device in the pilot circuit is about 5000 ohms, a high ohmic resistor 490 of about 50,000 ohms may be chosen.

The actuating motor 44| is of the reversible type. Its direction of operation is controlled by a reversing switch 459 which, depending on its position, connects either lead 485 or 485' with the relay contact 427. A second reversing switch 458' is coupled with switch `459, as is indicated by a dot-and-dash line. Switch 459 reverses the leads 429 as totheir connection with the relay 425. 4Switches 459 and 459 permit adjusting the actuating means 44| at will or automatically to operate in either direction.

It will be seen that despite the different construction oi the measuring system according to Fig. 4 as compared with the-system previously described, the operations of the two systems are similar as 'regards the essential features of the invention.

Fig. '5 exemplifies a system for controlling a mechanism in dependence upon two variable voltages. The illustrated system serves forde- Anl electric .motor or some other motorio means .may be usedor this purpose.

The just-mentioned measuring and relay cir- .cuit is not of the balanceable type but involves a threshold principle. That is, the relay 5I5 has from stationary contact 5| 1 to stationary contact 5|8. Assuming a proper direction of rotation of the contact ,5I4, the voltage drop across relay 5 I 5 is below the threshold or minimum value when the contact begins its cycle of operation. During its path of travel, the contact will reach a resistance step of resistor 5|3 where the relay voltage passes beyond the threshold value. Consequently, at this moment the relay will respond, the phase position of the contact in this instant being respective of the voltage diil'erence of elements 5I I and 5I2. The resistance steps of resistor 5I3 are preferably so dimensioned that their resistance value increases in each subsequent step along the path of contact motion; an increase of the resistance steps in accordance with an inverse hyperbolic law is especially favorable as is explained in detail in my copending application, Serial No. 402,170, led July 12, 1941, now to issue as Patent No. 2,303,391.

The thermocouple 52| is also directly connected with a second potentiometer resistor 523 whose slide contact 524 is series connected with a relay 525 and a current source 530 for providing a bucking voltage. The arrangement is such that the circuit represents a balanceable potentiometric network so that a reversal of the current occurs in the branch of the relay 525 when the contact 524 passes through a balance point whose position relative to the resistor ,523 depends upon the magnitude of the voltage supplied by the thermoelement 52|. The contact 524 is connected with termining the critical temperatures of steel by comparing a specimen X with a standard piece of porcelain or another material, such as nickel.

nected with the other pole of the same relay..

The resistor 5I3 is subdivided into a number of steps so that the contact 5|4, during its operation, changes the voltage drop eiective across the relay 5 I5 in steps corresponding tothe gradation of the resistor 5I3. The potentiometer is of the circular typeand the shaft 532 of the rotary contact 5I4 is driven by a motorie device 53|.

a stylus electrode 444 of a recording device, and both are actuated by means of a worm shaft 542 under control of an intermediate step drive 54|. rI'he drum` member of the recording device is designated by 545.

A discharge circuit containing a capacitor 583, a current source 58|, and a resistor 582 is connected through leads 584, 585, and 581 with the recording device and the step drive through the movable contact 528 and the stationary contact 521l of the relay 525, a short circuit path 588 containing a high ohmic resistance 590 being connected in parallel to the recording device and the step drive'.

Connected with the pilot circuit is also a relay 580 of the retarded type in series arrangement with a rotary reversing switch 508 with two switching positions. In the illustrated position, relay 500 is connected with lead 585 to run the actuating device in one direction. In the other position of switch 508, relay 500 is connected with lead 585' to cause device 54| to operate in the other direction. 'I'he switch 508 is controlled by the relay armature 508 in cooperation with a coupling 509 and a drive 5| 0. The operation of these elements will be explained in a later place. Assuming for the present that during a given periodthe coupling 508 is kept disengaged by relay 500 and the switch 508 is at rest in the illustrated position, it will be recognized that the operations of pilot circuit and recording device are similar to those of the corresponding parts of the other embodiments despite the fact that the variable circuit elements supply voltages and are connected in measuring arrangements different from those previously described.

i anceable .potentiometric network containing the potentiometer resistor lll and its movable contact Il in series connection with a relay I5 and a source 52| of a bucking voltage. The contact III is carried by a holder 532 which is periodically reciprocated alongthe resistor GII by means of a transmission 822 driven by a suitable motorio device 52|. The pressure gauge 62| acts on ,the movable contact 625 of a differential relay 525. "An armature 55| also connected with the movable relay contact 525 'and controlled by a magnet coil B52, serves to supply the counteracting force for operating the relay. 'I'he coil 652 is connected in an adjusting circuit which is energized from the line 81| and contains two constant resistors 553 and 555 and a variable impedance member 554 consisting for instance of a variable inductance. By varying the eil'ective impedance value of member 654, the energizetlon of the coil 552 is changed correspondingly so as to balance the ell'ectof the pressure gauge in a position of adjustment of the element 654 which is indicative of the pressure magnitude to be determined. It will be seen that the measuring arrangement containing a pressure gauge is again different from all o! those previously described. In the system o! Fig. 6, a balance is obtained not within an electric circuit but within a mechanically operating relay mechanism. However, this arrangement has also the effect o! controlling a relay in a moment when an adiusted program magnitude becomes equal or assumes a predetermined ratio to the variable control magnitude.

The rest of the system shown in Fig. 6 is substantially similar to those previously described. The drive means of contact Bil are connected with the drive element 292 of the stylus electrode 544 of a recording device, while the drum member |45 oi' this recorder is actuated in synchronism with the adiustable impedance member 554 by means of a step switch 681 connected with the drum and the impedance member by shafts 565 and 55B respectively. 'I'he recording device in Fig. 6 is shown in a lateral view so that the periodio and oscillatory motion of the stylus 544 occurs in a direction perpendicular to the plane of illustration. 'I'he pilot and discharge circuits controlled by relays SI5 and 525 contain a capacitor 553. a current source 65|, a resistor 552, a shunt path 85| and the leads 684, 585, and 85, these elements being connected with each other and with the recorder and the step drive in a manner similar to the corresponding parts of the systems previouslyy discussed.

When describing the foregoing embodiments. it has been assumed for the sake of simplicity that the intermedlately operating actuating means consist of a switch-like device which moves the appertaining potentiometer contact and stylus electrode step by step each time a control impulse is supplied to the actuating device. Although it is possible and advantageous, as regards some uses oi' systems according to the invention,

to energize the actuating means directly by the control impulse supplied by the pilot circuit, as

is illustrated 6 (element lll). it is Irequently desired to operate with relatively weak currents in the pilot circuit and to control relatively high torques. For this reason, it is preferable to provide the intermediate actuating meanswith an auxiliary energy source and to use the pilot circuit only for-governing the eilect oi' this source. Fig. 7. It is assumed that the illustrated mechanism forms parto! the system of Fig. 2 and that the actuating device serves for rotating the worm shaft 242 carrying the reciprocable holder 242 with the potentiometer contact 224 and the stylus electrode 2 44. According to Fig. 7, the shaft 242 is rotated by means of a, bevel gear 251 which in turn is driven by a driving gear 255. 'I'he latter gear is actuated by a clockwork, electric motor, or an'y other suitable auxiliary energysource.

` Coupled with the mechanism is also a Bear 252 meshing with one of the wheels of the bevel gear and carrying a, cam 260 with one notch engaged by a detent 256. A magnet coil 255 connected with the leads 285 and 285 o! the pilot circuit serves to release the detent when energized by a control impulse. The release of the detent has the etl'ect thatthe cam 260 and the gear 2l are permitted to perform a single rotation corresponding to one step of progression of the potentiometer contact. The controlling energy for operating such a relay type oi' device is very low so that the dimensions of the discharge circuit can be kept within convenient limits.

When describing the system represented by Figs. l, 2 and 3, it is assumed in the foregoing that the phenomenon to be observed is controllable as to the direction of its change and that the slow-acting of the two measuring arrangements is adjusted, as to its sense of progression, to that direction. However, it is also an object of my invention to provide systems of the type here described, which involve a reversible automatic operation so as to respond to control magnitudes of varying direction. The means according -to the invention for achieving such an operation will be explained presently.

Referring to Fig. 2, for instance, it is obvious that the cyclically operating potentiometer 2I2, 2I4 and the appertaining measuring device will cause the relayV 2i 5 to respond to the instants neous magnitude to be measured by variable element 2II regardless o! whether the magnitude increases or decreases and despite the fact that the sense of rotation of the potentiometer contact 2I4 remains the same. Hence, this part of the system is inherently capable oi' responding properly to directional changes oi.' the controlling magnitude. In contrast thereto. the second measuring device containing the variable element 22| requires for its proper operation a direction of contact motion depending on the direction of change of the appertaining control magnitude. If the magnitude reverses its direction of change while the system is in operation, the independ-J ently operating potentiometer 2Il, 2 I 4 would continue to actuate its relay 2I5, but the programmatlcally operating arrangement would keep ita relay 225 inactive and thus stop operating until the change of the magnitude of element 22| has againv assumed lthe original' direction and progresses up to the program value prescribed by contact 224.

It follows from the foregoing that in order to render such a system capable of reversible opera tion, merely the last-mentioned potentioinetrie` An example o! this type is shown iny sion of its motion. This may be eifected, according to the invention, in two different ways. One way is to control the actuating means of this potentiometer indirectly, in particular by reversing the direction of its motion in response to the cessation of the proper operation of the system.

The other way is to effect a direct control by reversing the motioniin immediate response to directional changes of the primary control magni- 'tude. These two aspects of the invention are as to .actuate the rotary reversing switch 505 in given intervals. That is, this drive tends to reverse in regular intervals the direction of motion of the actuating device 54| and the assembly 524, 544 driven thereby. A reversal of switch 505, however, occurs only if coupling 509 is closed at the propermoment but does not take place if the coupling is disengaged. The relay armature 500' is spring-biased and causes the coupling 509 to establish a driving connection between drive 5|0 and switch 508. When attracted .by the relay 500, asis shown in Fig. 5, the armature disengages the coupling 509. Relay 500 -s a time relay and hence keeps the\coup1ing disengaged for a given period afterV each energization of the relay, the time constant being so chosen that the period of retardation is safely longer than the longest period of time which normally elapses between two subsequent recording operations, i. e., subsequent operations of the pilot circuit.

The showing of switch 500 in Fig.,5 is simpliiled for reasons of illustration. As to details of this switch, reference should be had to Fig. 8 representing the switch 508 with all necessary contacts and connections. The switch has a rotary contact member E mounted on the shaft F controlled by the.coupling 509 (in Fig. 5). Member E carries a contact bridge M which in one position connects contacts H and I, and, in its other position, i. e., rotated 180 into the position M', connects contacts H and I. Thedirection of rotation is marked by arrow G. Two contacts K and K are connected through a current source L with lead 585 of the pilot circuit. Contacts H and Ht are connected with leads 555 and 585 respectively, and contacts I and I are connected with the retarded relay 500.

The reversing device operates as follows. Let us consider a moment in`which an increasing magnitude of element 52| is being recorded with the reversing control elements 500, 508, 509 and 500 in the illustrated positions (Figs. 5 and lEl), armature 500 still being attracted due to a recent energization of relay 500. Now, before the period of retarded action oi armature 500' elapses, a new control impulse occurs in the pilot circuit and energizes relay 500. As a result, a new retarding. period starts running. This is repeated as long as the magnitude of element 52| continues to increase. Hence, the coupling -509 remains disengaged and the switch 500 stays inoperative during the entire period just discussed.

Let us now assume that the measuring magnitude vof element 52| has reached its peak value and starts declining. Then, no control impulse will pass through the pilot circuit for the/ reason explained previously. After elapse of the period of retarded action. armature 500 drops olf and caus coupling 509 'to establish a driving con# nection between drive 5|0 and switch' 508. The next driving impulse caused by drive 5|0 will then turn the switch placing contact bridge M- in the position M' (Fig. 8) In this position, lead 555 is disconnected While the pilot circuit from relay 500 now extends over lead 585' to device 54 I. That is, the direction of ,motion of device 54| is now reversed. Before reaching the position M'-, the contact bridge M forms a temporary connec tion between contacts K' and H and thus connects the current source L with' lead 505. The resulting energizing impulse, passed through device 54| causes the latter to move one step in the f.

direction opposite to that of its preceding opera tion. -Due to 'this backward motion, the contact catches up with the declining value oi' the magsnitude of element 52|,.or rather moves to a program point below that magnitude. Wh'en, now, the declining control magnitude reaches the balance value corresponding to the new position of contact 52,4, a control impulse is passed through the pilot circuit and causes the recorder to produce a recording mark and the actuating device 54| to move the contact 524 and stylus 544 one step farther in the direction of decline of the control magnitude. As long as new control impulses are issued at a suiicient frequency, the coupling 509 remains again ineii'ective and the switch 500 at rest in its reversed position. If the impulses cease to recur, the drive 5|0 becomes eilective and returns switch 500 into the original position by rotating it another 180 in the direction of the arrow G. During this rotation, a temporary connection is established between contacts K and H, ,thereby causing the contact 524 to catch up with the control magnitude in a manner similar to that described above, except that now the motion is in the opposite direction.

fIhe current source L may supply an intermittent current if it is desired to have the contact 2|4 move more than one step after each reversal of its direction of motion. The reversing switch 500 may also be coupled with the drive of the potentiometer contact 5| 4 so that a separate driving motor is dispensed with and the mechanical partot the system designed as a structural unit. It will also be apparent that other types of time relays may be used, or that the mechanically operated coupling 509 may be replaced by an electric control of the switch, the relay armature 500 then being used as a movable control contact.

While systems of the type just described respond toup and down movements of the controlling magnitudes, they require a timing, within limits, of some of their members to the expected rate of change of the control magnitudes. or Vice versa. These timing conditions can, as a rule, be complied with where the phenomena under observation are bound to occur slowly or within known or controllable limits of their rate of change. This is the case, for instance, when controlling or recording the operation of inclusn trial. furnaces, heating plants or other heat-operated systems which, due to their thermal capacity, exclude desultory changes of temperature. Similar conditions prevail when recording` the energy requirements of a. factory, the energy output of a power station, or when determining the measuring magnitudes of a controllable test such as the one described in conjunction with Fig. l.

When such requirements cannot be met, or when a measuring system for magnitudes with a wider range of admissible rates of change is desired, or when desultory changes of the control 'magnitudes are to be responded to, a more direct control of the operating direction may be employed. The system shown in Fig. 9 exemplifies a control of this type.

According to Fig. 9, the two variable control elements 9I| and 92| are connected in two bridge circuits respectively. The first circuit contains the element 9| I in series with a constant resistor 9|2 and a slide wire resistor 9I9 whose movable contact 9H lies in the zero branch 9|9 together with a relay 9I5. Contact 9H is rotated by a shaft 992 connected with a. recording drum 946 which in turn is driven by a. synchronous motor 99| fed from the line 91| through leads 912.

tion shown in' the drawings, a shunt path 999, 999

Hence, contact 9H and drum 996 rotate periodically in synchronism with each other, The second bridge circuit contains element 92| in series with a constant resistor 922 and a potentiometric balancing resistor 923. The movable potentiometer contact 929 is series connected with a relay 926' in the zero branch 929, and is mounted on a holder 999 of a stylus electrode 94|. Contact 92| and stylus electrode 944 are reciprocated by a worm shaft 942 driven by a reversible motor 94|, also fed from the line 91|. The line also feeds the two measuring bridges through leads 919, 911

and 919.

The construction and operation of the system thus far described are similar to the corresponding parts of the system shown in Fig. 2, with the essential exception that the resistor 929 is not necessarily divided into steps and that the drive eflected by motor 94| is not limited to one step at a time but may cover the whole path of motion in a continuous or intermittent operation. Motor 94| is controlled by the amature 929' in cooperation with the stationary contacts 921' and 929' of relay 929'.. Motor 99| turns in one direction when contact 926' engages 921', as shown. and in the opposite direction when contact 926 engages 229'. Motor 99| is at rest when contact 929' is ln the intermediate position, l. e., when the bridge is balanced and the zero branch 929 not energized, a polarized three-pomtion relay 929' being used to obtain this operation.

When in operation, the relay armature 926 is in the neutral position and the contact assembly 929. 999, 9 at rest as long as the position of the assembly corresponds to the control magnitude supplied by element 92|. When the magnitude changes, the zero branch 929 draws a current in either direction and causes relay 926' to energize the motor 96| over either contact 921' or 929'. Motor 99| now eilects a follow-up movement tending to re-establish the balance condition of the bridge circuit. Hence. this device has always the tendency to keep stylus 9" in a balance-responsive position where the pilot circuit,

described presently, is in condition to respond to the relay 9|6 of potentiometer contact 9H,

The pilot circuit, connected to contacts 9|6, 9I1 and 9|6 of relay 9|9, is associated with a capacitive discharge circuit 99|, 992 and 999 similar to those of the preceding embodiments. and extends over leads 999, 996 and 991 through the contact assembly 926, 921 and 929 of a relay 926 and the electrode members 9 and 949 oi theI recording mechanism. l`Relay 926 lies in a circuit which contains a current source 919 and a contactor 999 controlled by the armature 926. 'I'his circuit is closed when the amature 929 is in the balance-responsive, i. e., neutral, position and open when the amature 926' engages either conretarded type so'as to keep contact 926 in engagement with contact 921 fora given period after each energization, this period being preferably longer than one full cycle of rotating contact 9I9.A

When armature 926 is in the non-responsive DoSi lies across the pilot leads'99l and 991 in order to block a discharge oi the capacitor through the recording mechanism.

96| denotes the drive motor of a time-marking device. The motor is energized through leads 999 from line 91|, and rotates a cam gear 969 in pro` portion to time. The cam controls a contact 999 intermittently in equal intervals of time and thereby causes an auxiliary capacitive circuit 99|', 992'. 993 to be alternatively charged and discharged. ,The discharge passage through connections 966' and 991 into the pilot circuit and the recorder members 9M and 945. As a result, a number of time marks are superimposed on the record, as will presently be explained more in detail.

When in operation, the stylus 9 is usually in balance position, the contactor 969 closed, relay 925 energized, and contact 926 in engagement with contact 921. As soon as the periodicalLv operating potentiometer contact 9H passes through the balance point, relay 9|5 causes movable contact 9I6 to switch over to contact 9|9 and to discharge capacitor 969 through 9M, 926. 921, 999. 995, 9 and 991. This causes the stylus 9 to produce a mark on a discharge-responsive recording sheet placed on the drum electrode 996. When the response of relay 9i! occurs while contact 9 is just performing a follow-up motion, the contactor 969 is in open position and relay 925 apt to be already de-energized. If this is the case, the discharge from capacitor 999 is bypassed at 929, 921 through path 999, 999, and remains without eil'ect on the recording mechanism.

The resulting record, as shown in Fig. l0, is represented on the recording sheet 999 by a train of marks 996 which form a curve which is indicative of the two variable magnitudes supplied by elements 9I| and 92|. Since the time-marking device is connected with the same recorder electrodes, the time marks 991 appear superposed on. or in proximity to, the recorded curve and thus indicate directly the proper correiation of the time marks to the corresponding points of the curve. The discharge circuit of the time-marking device is preferably designed to supply an electrode voltage or current higher than that of the other discharge circuit s0 that the time marks 991 are clearly distinguished from those of the curve by having a larger diameter.

The time-marking feature of the system of Fig. 9 is related to disclosure in my copending application entitled Three-magnitude recorder." Serial No. 470,440, iiled December 29, 1942.

The use of a follow-up principle in one of the two measuring devices of a system according to Fig. 9 has the advantage that it lends itself readily to be being controlled by fast-changing or desultorytphenomena. One ot its characteristics is also that the speed of rotation of the periodically operating potentiometer is largely independent of the operation of the follow-up device and may be varied Within very wide limita For instance, a relatively slow-acting potentiometer drive may be applied.

I claim:

tact 921' or 929'. Relay 929 is preferably of the 1l l. lin an electric system for controlling s accenna .mechanism in dependence upon a function of two variable control quantities, said mechanism having two cooperative members each being movable at an angle to the motion of the other, an impulse-transmitting pilot circuit connected with said mechanism for rendering said members operative when they are in a relative position substantially corresponding to said function, two measuring devices each containing a variable element responsive to one of said quantities respectively and an independently variable element and having a relay connected with said two elements to be diierentially controlled by lboth so as to respond to the passage of their differential control eilect through a given differential value, said relays being both arranged in said pilot circuit for controlling said circuit to become operative when both relays are in responsive condition, cyclically operating drive means for actuating one of said mechanism members and said independently variable element of one of said measuring devices in synchronism with each other so as to establish said differential value in said one device whenever said mechanism member passes through a position indicative of said variable control magnitude eiiective in said one device, stepwise operating actuating means for actuating the other mechanism member and said independently variable element of said other measuring device in synchronism with each other so as to establish said diilerential value in said other device whenever the position of said other mechanism member is indicative of said other control magnitude, said actuating means being connected with said pilot circuit to be controlled thereby so as to move one step each time said mechanism becomes operative.

2. An electric system for recording a function of two variable quantities, comprising in combination a recording device having a rotary member for accommodating a recording sheet and a stylus member movable relative to said rotary member for producing a record on said sheet, two balanceable measuring devices each including a variable control element responsive to one of said quantities respectively and an independently variable balancing element and having a relay connected with said two elements and controlled thereby so as to respond to the passage of the ratio of the control eiects of said elements through a given value, periodically operating drive means for varying said balancing element of one of said devices in synchronism with the rotation of said rotary recorder member, actuating means for varying said balancing' member of said other device in synchronism with the motion of said stylus member, the operating periods of said drive means and actuating means respectively being diilerent from each other so that one of said means completes one cycle in a period of time including a multitude of complete cycles of the other means, and an impulse-transmitting pilot circuit connected with said recording device to be jointly controlled by said two relays for causing -said stylus member to effect a recording mark at the moment when both relays are placed in responsive condition.

3. An electric system for recording a function of two variable contro1 quantities, comprising in combination a recording device having a rotary member for accommodating a recording sheet and a stylus member movable relative to said rotary member for producing a record on said to one of said quantities respectively and an inl dependently variable balancing element and having a relay connected with said two elements' so as to be controlled by both in response to the passage "of their contro1 effects through a given ratio periodically operating drive means for varying said balancing element of one of said devices in. synchronism with the rotation of said rotary recorder member, stepwise operating means for actuating said balancing memberof said other and said stylus intermittently and in synchronism with each other, the operating period of said actuating means for completing one step of actuation -belngtimed to include at least one full operating period of said drive means, an impulse-transmitting pilot circuit connected with said recording device and controlled by said two relays for causing said stylus member to effect a recording mark at the moment when both relays are placed in responsive condition.

4. An electric System for recording a function of two variable control quantities, comprising in combination a recording device having a rotary member for accommodating a recording sheet and a stylus member movable relative to said rotary member for producing a record on said sheet, two balanceable measuring circuits each including a variable circuit element responsive to one of said quantities respectively and a potenu tiometric balancing device and having a relay connected with both said element and said pon tentiometric devicegso as to be responsive to 'the balance condition of said measuring circuit, peri.- odically operating drive means for operating said rotary member and one of said potentiometric devices in synchronism with each other, stepwiseoperating actuating means connected with said stylus and said other potentiometric device for moving them intermittently in synchronism with. each other, said actuating means having an op erating period, as regards the completion of a full cycle of operative steps, winch includes a multitude of full-cycle operating periods of said drive means, and an impulse-transmitting pilot circuitoonnected with said recording device and controlled by said relays of both said measuring devices for causing said stylus member to ehect a recording mark at the moment when both relays are placed in balance responsive condition.

5. An electric system for recording a function of two variable measuring quantities, comprising in combination a recorder having a rotary .member for accommodating a recording sheet and a reciprocatory stylus member relative to said drum member for producing recording marks on said sheet, two balanceable measuring devices each including a variable contro1 element responsive to one of said quantities respectively and an inde pendently variable balancing element and having a relay connected with said two elements so as to be differentially controlled thereby in response to the passage of their control effects through a given differential value, periodically operating drive means for varying said balancing element of one of said devices in synchronism with the motion of one of said recorder members, stepwise-operating actuating means connected with said other balancing element and said other recordel member for moving them intermittently in synchronism with each other over a graduated range of progression, an impulse-transmitting pilot circuit connected with said recorder and controlled by said two relays for causing said stylus member to produce a recording mark at the moment when both relays are placed in responsive condition, and control means connected with said actuating means for causing them to advance one step along their path of progression in dependence upon each recording operation oi said stylus member. A

6. An electric system for recording a function o! two variable measuring quantities-comprising inv combination a recorder having a rotary member for accommodating a discharge-responsive recording sheet and a reciprocatory stylus member movable relative to said rotary member for producing recording marks .on said sheet, said two recorder members forming electrodes ior passing a discharge through said sheet when energized. two adjustable measuring devices each including a variable control element operative in response to one o! said quantities respectively and a relay responsive to the adjustment ot the device indicative of said quantity, periodically operating drive means for varying the adjustment of one of said measuring devices in a given cycle in synchronism with the motion of one o! said recorder members, actuating means connected with said other measuring device and said other recorder member for varying their respective adjusthients in synchronism with each other, a pilot circuit connected between said two relays and said recorder for controlling the latter in dependence upon both relays being in responsive condition, current supply means and a capacitor connected with said pilot circuit through one of said relays whereby said capacitor is connected with said supply means for charging when said latter relay is in non-responsive condition and with said pilot circuit for discharge through said recorder members and sheet when said latter relay is in responsive condition, said other relay being arranged so as to block the discharge of said capacitor through said members as long as said other relay is in non-responsive condition.

7. A measuring system for determining a function oi two variable quantities, comprising in combination two measuring devices each having a variable measuring element responsive to one of said quantities respectively and an adjusting element variable independently oi' said quality and having a relay connected with said two elements so as to be controlled thereby in dependence upon said adjusting element passing through an adjustment indicative of said quantity, a mechanism having two cooperative members each being movable at an angle to the motion of the other, an impulse-transmitting pilot circuit connected with said mechanism for rendering said members operative when they are in a relative position substantially corresponding to said function, periodically operating drive means for actu ating one of said mechanism members and said adjusting element of one of said measuring devices in synchronism with each other, actuating means for actuating said other mechanism member and said adjusting element of said other measuring device in synchronism with each other, said pilot circuit being connected with said two relays so as to be controlled thereby to become operative when both relays are in responsive condition, and control means for causing said actuating means to effect a one-step motion in response to each operation ot said pilot circuit, whereby said mechanism is caused to operate in accordance with said function of said two variable quantities.

8. A measuring system for determining a func-V tion of two variable quantities, comprising in combination two measuring devices each having a variable control element operative in accordance with one of said quantities respectively and an adjusting elementyariable independently of said quantity, and including a relay connected with said two elements so as to be controlled by both in dependence upon said adjustable element passing through an adjustment indicative of said quantity,a mechanism having two cooperative members each being movable at an angle to the motion of the other, an impulse-transmitting pilot circuit connected with said mechanism for rendering said members operative when they are in a relative position substantially corresponding to said function, periodically operating drive means for actuating one of said mechanism members and said adjusting element ol one of said measuring devices in synchronism with each other, actuating means for actuating the other mechanism member and said adjusting element of said other measuring device in synchronism with each other, said pilot circuit being connected with said two relays so as to be controlled thereby to become operative when both relays are in responsive condition in order to cause said mechanism to operate in accordance with said function, and a. capacitive discharge circuit controlled by said relay of said devicev which has its adjusting element periodically actuated by said drive means, said discharge circuit including a current source and being connected with said latter relay and said pilot circuit so as to be charged when said latter relay is in non-responsive condition and discharged into said pilot circuitwhen said latter relay is in responsive condition, and a discharge path connected with said pilot circuit for short-circuiting said discharge in order to render it ineffective as regards said mechanism when said other relay is in nonresponsive condition. j

9. A measuring system for determining a function oi two variable quantities, comprising in combination two measuring devices each having a variable measuring element ior` producing a control effect in laccordance with one oi said quantities respectively and an adjusting element for producing another control effect variable independently of said quantity, and including a relay connected with said two elements so as to be diiierentially controlled in dependence upon said two control effects in order to respond to the passage of said effect through a given difierential value, a mechanism having two cooperative members each being movable at an angle to the motion oi the other, an impulse-transmitting pilot circuit connected with said mechanism for rendering said members operative when they are in a relative position substantially corresponding to said function, periodically operating drive means for actuating one of said mechanism members and said adjusting element of one oi said measuring devices in synchronism with each other, reversible actuating means for actuating said other mechanism member and said adjusting element of said other device in synchronism with each other, said actuating means being controlled by said relay of said latter device so as to remain at rest, when the position of said latter mechanism member is indicative of said other control magnitude, and in motion in either direction for effecting a follow-up movement when said position is not in accordance with said other control magnitude, said pilot circuit being connected with said two relays so as to be controlled thereby when both are in responsive condition, whereby said mechanism is caused to operate in accordance with said function oi said two variable magnitudes.

10. A measuring system for determining a function of two variable magnitudes, comprising in combination two measuring devices each having a variable control element for producing a control effect responsive to one of said quantities respectively and an adjusting elementy for producing another control effect variable independently of said quantity, and including a relay connected with said two elements so as to be controlled by said two control effects in order to become operative in dependence upon said adjustable element passing through the adjustment indicative of said one quantity, a recording mechanism having two cooperative members each being movable at an angle to the motion of the other, an impulsetransmitting pilot circuit connected with said mechanism for rendering said members operative when they are in a relative position substantially corresponding to said function, periodically operating drive means for actuating one of said mechanism members and said adjusting element of one of said measuring devices in synchronism with each other, actuating means for actuating the other mechanism member and said adjusting element of said other measuring device in synchronism with each other, said pilot circuit being connected with said two relays so as to be controlled thereby in order to become operative when both are placed in responsive condition whereby said mechanism is caused to produce a record representing a function of said two variable magnitudes, and timing means associated with said recording mechanism for placing time marks on said record of said function, said timing means comprising a control device operating in proportion to time and intermittently operating marking means for producing said time marks in given intervals of time independent of the variations of said two quantities.

11. In an electric recording system as set forth in claim 2, a time marking device associated with said recording device and comprising another stylus member reciprocable along said rotary member, means in driving connection with said other stylus member for actuating it in proportion to time so as to produce time marks on the aforesaid recording sheet of said recordingl device in given intervals independently of the operation of said inst-mentioned stylus member.

12. In a system as set forth in claim 2, time marking means associated with said recording device and comprising a time marker circuit connected with said recording device, and means operating in proportion to time for energizing said latter circuit in given intervals of time4 so as to cause said stylus member to superimpose on said recording spaced time marks independently of the variations of said two control magnitudes.

13. An electric system for recording a function o! the quantities of two variable phenomena, comprising in combination a recording device having a rotary member for accommodating a recording sheet and a stylus member movable relative to said rotary member for producing a record on said sheet, two balanceable measuring devices each including a variable control element responsive to one of said quantities respectively and an independently variable balancing element and having a relay connected with said two elements and controlled by both so as to assume a given condition when the control effects of said two elements as regards said relay pass through` a given ratio, periodically operating drive means for varyingsaid balancing element of one oi said devices in synchronism with the rotation of said rotary recorder'member, a step-switch in driving connection with said .balancing element of said other device and said stylus for actuating said balancing member and said stylus intermittentlyand in synchronism with each other, an impulsetransmitting pilot circuit connected with said recording device and controlled by said two relays for causing said stylus member to effect a recording mark at the moment when both relays are in said given condition, said step-switch being electrically connected with said pilot circuit to be controlled by the latter to progress one step each time said stylus has effected a recording mark.

14. In a system for controlling the operation of a mechanism in accordance with a function of the quantities of two variable phenomena, said mechanism having two normally idle running members arranged in cooperative relation for performing together, when actuated, the operation to be controlled, each of said members being movable at an angle to the motion of the other, pilot means for actuating said members at points of their relative travel corresponding to said function, two devices for measuring said quantities respectively, each device having a driven adjusting member movable over a range which includes an adjusting position indicative of said respective quantity, drive means for moving one of said mechanism members and one of said adjusting members in synchronism with each other, actuating means for moving said other mechanism member and said other adjusting member in synchronism with each other, and relay means connecting said pilot means with said two devices so as to render said pilot means operative when said adjusting members are simultaneously in said respective positions.

15. A system for controlling the operation of an electrically actuated mechanism in accord.- ance with a function of the quantities of two variable phenomena, comprising in combination two measuring devices each including a variable control element for measuring the quantity of one of said phenomena respectively and an adjustable balancing element and having a relay connected with said two elements and controlled thereby so as to assume a given condition when the control eiects of said elements on said relay pass through a given differential value, drive means connected with said balancing element or" one oi' said devices for varying the adjustment of said latter element independently of the variations of said appertaining control elementy actuating means connected with said balancing eiement of said other device for varying the adjustment of said latter element, said mechanism to be controlled having two movable members arranged in cooperative relationship for performing together, when electrically actuated, the operation to be controlled, each of said mechanism members having a path of motion extending at an angle to that of the otherv and being connected with one of said drive means and actuating means respectively to move in synchronism therewith, and an electric pilot circuit connected between said relays and said mechanism and controlled by said relays to electrically actuate said members when both said relays are in said given position.

16. A. system for controlling the operation of an electrically actuated mechanism in accordance with a Vfunction of the quantities of two variable phenomena, comprising in combination two balanceable measuring devices each including a. variable control element for measuring the quantity of one of said phenomena respectively and an adjustable balancing element and having a relay connected with said two elements and controlled thereby so as to assume a given condition when the control effects of said elements on said relay pass through a given ratio, cyclically operating drive means connected with said balancing element of one of said devices for varying the adjustment of said latter element independently of the variations of said appertaining control element, actuating means connected with said balancing element of said other device for varying the adjustment of said latter element, an electric pilot circuit connected between said two relays and said actuating means for controlling said actuating means in dependence upon both said relays being in said given condition. said mechanism to be controlled having two movable members arranged in cooperative relationship for performing together, when electrically actuated, said mechanism operation to be controlled, each of said mechanism members having a path of motion extending at an angle to that of the other and being connected with one of said drive means and actuating means respectively to move invsynchronism therewith, and said pilot circuit being also connected with said mechanism to electric ally actuate said members when both said relays are in said given condition.

i7. A system for controlling the operation of an electrically actuable mechanism in accordance with affunction of two variable phenomena, comprising in combination two balanceable electric circuits each including a variable circuit element for measuring the variations of one of said phenomena respectively and an adiustable balancing element and having a relay connected with said two elements to be differentially controlled thereby in order to assume a given condition when their control effects pass through the balance condition, drive means connected with said balancing element of one of said circuits for varying its adjustment independently of the variations of said appertaining circuit element over a given range including the balance condition of said circuit, actuating means connected with said balancing element of said other circuit for varying the adjustment of said latter element over a range including the balance condition of said latter circuit, said mechanism to be controlled having two cooperative movable members for performing together, when electrically actuated, said mechanism operation to be controlled, each of said mechanism members having a path of motion extending at an angle to that of the other and being connected with one of said drive means and actuating means respectively to move in synchronismtherewith and an electric pilot circuit connected between said two relays and said mechanism for actuating said mechanism members when both said relays are in said given condition.

18. A system for controlling the operation of an electrically actuable mechanism in accordance with a function of two variable phenomena, comprising in combination two balanceable electric circuits each including a variable circuit element for measuring the variations of one of said phenomena respectively and having an adjustable potentiometric device and a relay connected with said circuit .element so that said relay is dinerentially controlled by both said element and said device in order to assume a given relay condition when the two control effects pass through a given differential value, drive means connected with' one of said potentiometric devices for varying its adjustment independently of the variations of said appertaining circuit element, actuating means connected with said other potentiometric device for varying its adjustment, an electric pilot circuit connected with said two relays so as to be operative only when both relays are simultaneously in said given condition, said -mechanism to be controlled having two cooperative members for performing together, when electrically actuated, said mechanism operation to be controlled, each of said mechanism members being movable at an angle to the motion of the other, control means connected with one of said members for moving it in synchronism with said drive means, and other control means connected with said other member for moving it in synchronism with said actuating means, said pilot circuit being connected with said mechanism to electrically actuate said members when said pilot circuit is rendered operative by said relays.

19. A system for controlling the operation of an electrically actuated mechanism in accordance with a function of two variable phenomena, comprising in combination two balanceable electric measuring circuits each including a variable circuit element responsive to variations of one of said phenomena respectively and an adjustable balancing element and having a relay connected with said two elements and controlled by both so as to assume a given condition when the two effects pass through a given differential value, drive means connected with one of said balancing elements to vary its adjustment independently of the variations of said appertaining circuit element, actuating means connected with said other balancing element for varying its adjustment, an electric pilot circuit connected with said two relays so as to be controlled thereby to become operative only when both relays are in said given condition, said mechanism to be controlled having two cooperative members for performing together, when electrically actuated, said mechanism operation to be controlled, each of said mechanism members being movable at an angle to the motion of the other, separate control means connected with said two members respectively for moving them in synchronism with the adjustment of said two respective balancing elements, said pilot circuit being connected with said actuating means and also with said mechanism for rendering said actuating means operative and actuating said mechanism members when said pilot circuit is rendered operative by said relays.

20. In an electric system for controlling the operation o f a mechanism in dependence upon a function of the quantities of two variable phenomena, said mechanism having two members arranged in cooperative relationship to each other for performing when actuated electrically, the operation to be controlled, each of said members being movable at an angle to the motion of the other, an impulse-transmitting pilot circuit connected with said mechanism for electrically actuating said mechanism when said members are in a position relative to each other substantially corresponding to said function, two measuring devices each containing a control element variable in accordance with one of said quantities respectively and an independently -givenconditommidother varlableelenentandhavingarelayconnected with both laid elements so controlledthereby in order to assume a given relay condition when the control eiIects of said elements pass through a given differential value, cyclically operating drive means for actuating one of said members and one of said y variable elements of one of said devicesin witheachotherso asto reptedly establish said differential value in said one device each me said mechanism member through a position indicative of said one a quantity, stepwise operating actuating means for actuating said other mechanism member and said independently variable element of said other m device in synchronism wltheachotherso astorepeatedlyestablish said differential value in said other device each time the positionotsaid otherm member is indicative oi said other quantity, and a discharge e circuit connected with said pilot circuit under motion of the other, an impune-transmitting pilot circuit conv said for electrically are in a position relative to each other substantially corresponding to said function, two measuring devices each containing a measuring element varying in accordance with one of said quantities respectively and an independently variable element and having a relay connected with both said variable element and having a relay connected with both said variable elements to be dierentially controlled thereby so as to assume a given relay condition when their control eiiects pass through a given differential value, said relays being both arranged in said pilot circuit for controlling said circuit to actuate said mechanism when both relays are in said given condition, cyclically Operating drive means for moving one of said mechanism members and actuating said independently variable element of one of said devices in synchronism with each other so as to establish said differential value in said device each time said mechanism member moves through a position indicative of said one quantity, stepwise operating actuating 'means for moving said other mechanism member and actuating said independently variable element of said other measuring device in synchronism with each other so as to establish diiierential value in said other device each time the position of said other mechanism member is indicative of said other quantity, said actuating means having a lower speed of operation than said drive means so that said drive means perform a multiple o! cycles while said actuating means pass once through their range of steps.

GEORGE KEINATH. 

